const someObject = {
  a: 1,
  perrito: 'Yolodog',
  aChar: 'a',
}

someObject[Symbol.iterator] = function() {
  let currentKey = 0;
  const keys = Object.keys(this);
  const { length } = keys;
  return {
    next: function() {
      return currentKey < length
      ? { value: this[keys[currentKey++]], done: false }
      : { done: true };
    }.bind(this),
  };
};

for (let item of someObject) { console.log(item); }
// 1
// Yolodog
// a